Found in JMeter 2.0 Using the HTTP Sampler with the 'Retrieve all embedded resources from HTML Files' ticked. When a resource that does not have a content type defined on the web sever is accessed a null pointer exception occurs on line 563 of HTTPSampler. Tracked this down to res.getDataType() being called, which uses a private string dataType in SampleResult that is not initialised. I have fixed this on my build by setting it to "" on initialisation and this works.
Thanks for reporting this. Fixed by making getDataType the parameter for the equals() method, rather than the object. [This allows dataType to be null - if this proves necessary...]
This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/1341